Fourier Transform Infrared (FTIR) Spectroscopy as a Utilitarian Tool for the Routine Determination of Acidity in Ester-Based Oils

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• 作者：Xianghe Meng ; Lei Li ; Qin Ye ; Frederik van de Voort
• 刊名：Journal of Agricultural and Food Chemistry
• 出版年：2015
• 出版时间：September 23, 2015
• 年：2015
• 卷：63
• 期：37
• 页码：8333-8338
• 全文大小：321K
• ISSN：1520-5118

文摘

A primary Fourier transform infrared (FTIR) method capable of determining acidity in ester-based oils is described and evaluated. Absolute free fatty acid (%FFA) and acid value (AV) calibrations were devised by spiking oleic acid into a refined, acid-free oil and measuring 谓_{COO^鈥?/sup>} at 鈭?569 and 谓_{phenolate^鈥?/sup>} at 鈭?588 cm^鈥?, respectively, in the second-derivative differential spectra. The FTIR acidity predictions were compared to the AOCS titrimetric method using acid mixtures as well as acid containing used vendor oils of undefined makeup and provenance, using two spectroscopically divergent reference oils as AC₀. Relative to the AOCS reference method, the FTIR procedure was found to be both more accurate (卤0.107 vs 卤0.122) and reproducible (卤0.025 vs 卤 0.077) in determining %FFA and similar in predicting AV. The FTIR_phenolate method overcomes a variety of limitations of earlier FTIR-based methods, being particularly simple and well suited to routine, semiautomated acidity analysis of ester-based oils using a basic FTIR spectrometer.